Antibodies can be raised against modified DNA. We have previously prepared and purified antibodies against ultraviolet photoproducts in DNA, both against pyrimidine dimers and against non-dimer photoproducts. The availability of antibodies against specific lesions in damaged DNA may enable development of radioimmunoassay methods to study both the damage and repair of DNA, with a sensitivity expected to be superior to that of other available methods currently being used for similar studies. We have prepared a new line of antigens, i.e., DNA modified by the carcinogen benzpyrene diol-epoxide I and by the carcinogen N-acetoxy N-acetylaminofluorene (AAAF), and have initiated the production of antibodies against these antigens in immunized rabbits. Antigens that are currently being prepared include gamma-irradiated DNA, DNA irradiated in a monochromator at several specific wavelengths, DNA modified by psoralen with subsequent near-light, and benzpyrene diol-epoxide specific adducts (e.g., A adduct and G adduct).